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Surgical Oncology

Ryan A. Lawless

INTRODUCTION

Test Taking Tips

  • Oncology questions can be quick points on the ABSITE, especially in the basic science portion of the exam.

  • Carcinoids and GISTs are still hot topics.

CELL CYCLE

In what phase of mitosis does the nucleus disappear?

  • Prophase

FIGURE 8-1

The cell cycle. The ability to microscopically recognize cells during both mitosis and DNA replication (by autoradiography after administering radiolabeled thymidine) led to the concept of the cell “cycle.” In this concept, new interphase cells undergo a period after leaving mitosis and before starting DNA synthesis called the first gap, or G1. Another gap, G2, occurs after DNA replication and before the next mitotic prophase. After mitosis, both new cells repeat this cycle. In rapidly dividing cells, G1 is a period in which cells accumulate the enzymes and nucleotides required for DNA replication, S is the period devoted primarily to DNA replication, G2 is a usually short period of preparation for mitosis, and M includes all phases of mitosis itself. In rapidly growing human tissues, the cell cycle varies from 24 to 36 hours. The length of G1 depends on many factors and is usually the longest and most variable period; the length of S is largely a function of the genome size. G2 and mitosis together normally last only 2 to 3 hours. (Reproduced with permission from Mescher AL. Junqueira’s Basic Histology: Text and Atlas, 15th ed. New York, NY: McGraw Hill; 2018.)

An illustration represents a Cell cycle. The cell cycle begins with the S phase which lasts for 8 hours which is followed by the G2 phase and mitosis that lasts between 2.5 to 3 hours. In the G2 phase, the cell is at the resting phase. Mitosis has four stages: Prophase, Metaphase, Anaphase, and Telophase. In prophase which takes approximately 1 hour, the chromosomes are aligned, and centrioles start moving to the opposite poles. In metaphase that takes less than an hour, the nuclear membrane disappears, chromosomes are aligned at the center, and spindle fibers form. In anaphase which takes less than half an hour, the spindle fibers pull the chromosomes towards the poles. In telophase that takes 1 minute, the cell divides into 2 daughter cells. Mitosis is followed by the G1 phase or interphase which lasts for 25 hours and leads to the S phase which again begins the cycle.
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In what phase of mitosis does chromosome alignment occur?

  • Metaphase

In what phase of mitosis do chromosomes separate?

  • Anaphase

In what phase of mitosis do nuclei form around replicated DNA?

  • Telophase

Name the purines:

  • Guanine, adenine

Name the pyrimidines:

  • Cytosine, thymidine, uracil

What is translation as it refers to the cell cycle?

  • Protein synthesis using an mRNA template by ribosomes

What is transcription as it refers to the cell cycle?

  • Synthesis of mRNA from DNA template by RNA polymerase

In what phase of the cell cycle do protein synthesis and chromosomal duplication occur?

  • S phase

In what phase of the cell cycle does mitosis occur?

  • M phase

TUMOR MARKERS

What tumor marker is associated with choriocarcinoma/testicular cancer?

  • β-Human chorionic gonadotropin (HCG)

What tumor marker is associated with colon cancer?

  • Carcinoembryonic antigen

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